News Release Number: STScI-2011-19

Neptune Completes Its First Circuit Around The Sun Since Its Discovery

July 12, 2011: These four images of Neptune were taken by NASA's Hubble
Space Telescope during the planet's 16-hour rotation. The
snapshots were taken at roughly four-hour intervals,
offering a full view of the blue-green planet. Today marks
Neptune's first orbit around the Sun since it was
discovered nearly 165 years ago. These images were taken to
commemorate the event.

The Hubble images, taken with the Wide Field Camera 3 on
June 25-26, reveal high-altitude clouds in the northern and
southern hemispheres. The clouds are composed of methane
ice crystals. In the Hubble images, absorption of red light
by methane in Neptune's atmosphere gives the planet its
distinctive aqua color. The clouds look pink because they
are reflecting near-infrared light. A faint, dark band near
the bottom of the southern hemisphere is probably caused by
a decrease in the hazes in the atmosphere that scatter blue
light. The band was imaged by NASA's Voyager 2 spacecraft in
1989, and may be tied to circumpolar circulation created by
high-velocity winds in that region. Neptune is the most
distant major planet in our solar system. German astronomer
Johann Galle discovered the planet on September 23, 1846. At
the time, the discovery doubled the size of the known solar
system. The planet is 2.8 billion miles (4.5 billion
kilometers) from the Sun, 30 times farther than Earth. Under the Sun's weak pull at that distance, Neptune plods along in its huge orbit, slowly completing one revolution approximately
every 165 years.